Ogive

An ogive (/ˈoʊdʒaɪv/ OH-jyve) is the roundly tapered end of a two-dimensional or three-dimensional object. Ogive curves and surfaces are used in engineering, architecture and woodworking. An ogive (/ˈoʊdʒaɪv/ OH-jyve) is the roundly tapered end of a two-dimensional or three-dimensional object. Ogive curves and surfaces are used in engineering, architecture and woodworking. The earliest use of the word ogive is found in the 13th century sketchbook of Villard de Honnecourt, from Picardy in northern France. The OED considers the French term's origin obscure; it might come from the Late Latin obviatacode: lat promoted to code: la , the feminine perfect passive participle of obviarecode: lat promoted to code: la , meaning the one who has met or encountered the other. However, Merriam-Webster's dictionary says it is from the 'Middle English oggif stone comprising an arch, from Middle French augive, ogivecode: fra promoted to code: fr diagonal arch'. In ballistics or aerodynamics, an ogive is a pointed, curved surface mainly used to form the approximately streamlined nose of a bullet or other projectile, reducing air resistance or the drag of air. In fact the French word ogive can be translated as 'nose cone' or 'warhead'. The traditional or secant ogive is a surface of revolution of the same curve that forms a Gothic arch; that is, a circular arc, of greater radius than the diameter of the cylindrical section ('shank'), is drawn from the edge of the shank until it intercepts the axis. If this arc is drawn so that it meets the shank at zero angle (that is, the distance of the centre of the arc from the axis, plus the radius of the shank, equals the radius of the arc), then it is called a tangent or spitzer ogive. This is a very common ogive for high velocity (supersonic) rifle bullets. The sharpness of this ogive is expressed by the ratio of its radius to the diameter of the cylinder; a value of one half being a hemispherical dome, and larger values being progressively more pointed. Values of 4 to 10 are commonly used in rifles, with 6 being the most common. Another common ogive for bullets is the elliptical ogive. This is a curve very similar to the spitzer ogive, except that the circular arc is replaced by an ellipse defined in such a way that it meets the axis at exactly 90°. This gives a somewhat rounded nose regardless of the sharpness ratio. An elliptical ogive is normally described in terms of the ratio of the length of the ogive to the diameter of the shank. A ratio of one half would be, once again, a hemisphere. Values close to 1 are common in practice. Elliptical ogives are mainly used in pistol bullets. Missiles and aircraft generally have much more complex ogives, such as the von Kármán ogive. One of the defining characteristics of Gothic architecture is the pointed or ogival arch.